It is proposed to investigate the mechanism in the strain-specific TA3-St murine mammary carcinoma ascites cell by which the cell-surface masking glycoprotein, epiglycanin, appears and strain specificity is lost. The biosynthetic pathway of the protein and carbohydrate moieties of epiglycanin and the inhibition of its synthesis will be studied. Investigation of the detailed carbohydrate structures and amino acid sequence of epiglycanin will be continued. Determination of the locations of the active carbohydrate and aino acid structures in the epiglycanin molecule will be performed by electron microscopy of complexes of specific lectins or antibodies with epiglycanin. The characteristics of glycoproteins, including epiglycanin, at the surfaces of oncorna virus particles budded from the TA3-Ha and TA3-St cells will be studied. By the use of radiolabelled antibodies to epiglycanin TA3-Ha tumors in the mouse will be used as a model in the development of a whole body scanning method for determining the exact location of cancer in the living organism. Studies of the masking mechanism will be performed by electron micrographs of TA3-Ha and TA3-St cells treated with ferritin-labeled antibodies to epiglycanin and H-2a antigens.